Well known examples of charged gas lighting instruments include neon lighted beer signs for smallscale, indoor application, and neon lighted billboards for outdoor, large-scale operation. Most often these type of charged gas lighting instruments utilize glass lighting tubes. The tubes are filled with an assortment of light emissive gas mixtures which often include neon gas. Depending on the mixtures, different colors of brightly glowing light, commonly referred to as "neon light," can be created when the gases contained in the glass tubes are subjected to an electrical discharge.
In most commercial settings (e.g., beer signs and billboards) the unprotected, glass tubes are secured to a frame, or in some cases, directly to the facade of a building for display. The fragile tubes, however, are highly susceptible to breaking. Indeed, quite often the tubes are damaged during shipping or installation procedures. Moreover, it is exceptionally difficult to reuse or relocate the tubes once they have been installed. When used outdoors, exposed tubes and their respective electrical fittings are extremely vulnerable to the outside elements. In addition, a charged gas lighting device, such as a neon light, utilizes a high voltage power source (e.g., 10,000 volts), and is therefore relatively dangerous. These devices should be installed and maintained only by a professional electric sign installer.
Various methods of protecting the glass tubes and electrical fittings are known in the art. They include U.S. Pat. No. 4,947,301 to Steele describing a non-conductive housing for sheltering the electrode ends and high voltage conductors of a neon tube; and U.S. Pat. Nos. 5,150,961 and 5,192,125 to Gonzalez describing apparatuses for illuminating a vehicle license plate including an annular neon tube mounted within a front transparent channel member and a rear protective cover plate.
There are various drawbacks, however, with the prior art. In particular, the apparatus as described in Steele mounts the neon tube to the housing exterior thereby exposing the fragile tube to the outside elements and greatly increasing the likelihood that the unprotected tube will be prematurely broken. The broken glass, or high voltage current from the wires attached to a damaged tube, poses a serious injury risk.
Even prior art devices which locate the neon tube within a housing do not eliminate the risk of high voltage shock. For instance, the apparatuses as described in the Gonzalez patents enclose the neon tube within a front transparent channel member and a rear protective cover plate. Although this protects an individual from accidentally touching the neon tube's high voltage electrical connections, the front and back covers create a seam through which a high voltage current may pass. That is, it is possible for electric current to arc from the electrical fittings through a seam in the housing. It is even more likely to occur if a conductive apparatus, like a metal screwdriver, is placed at or near the seam which is likely to occur during installation or maintenance procedures. In addition, electricity which arcs through a seam in the housing presents a serious fire hazard.
Also known in the art is U.S. Pat. No. 2,562,740 to Rizer describing a tubular florescent element covered by flexible plastic tubing also for illuminating a license plate. The flexible tube, however, does little to protect the neon tube from breaking upon a heavy impact, or insulate the electrical connections from delivering an electric shock.